[colr] Scale relative gradient coordinates and quantize clip boxes#1755
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LinearGradient.p2 and RadialGradient radiuses need to be computed in fontbe because we need the bounding boxes
Scale COLR gradient coordinates from percentages (0.0-1.0) to absolute font units using glyph bounding boxes. This fixes the core gradient geometry issue where Glyphs.app stores coordinates as percentages of the layer bounds.
Quantize COLR ClipBox coordinates to multiples of 1/10th of the font's UPEM (e.g. 100 units for 1000 upem etc.) to maximize clipbox reuse across glyphs. This matches ufo2ft/fontmake behavior and should reduce table size by allowing more glyphs to share the same ClipBox.
rsheeter
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Nov 14, 2025
rsheeter
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Love the extensive refs back to python!
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Scale COLR gradient coordinates from percentages (0.0-1.0) to absolute font units like Glyphs.app does, using the glyph bounding boxes. We do this in the backend to avoid having to compute these twice.
Also quantize COLR ClipBox coordinates to multiples of 1/10th of the font's UPEM (e.g. 100 units for 1000 upem etc.) to maximize clipbox reuse across glyphs, matching ufo2ft/fontmake behavior.
I would like to add more tailored unit tests but from local testing this patch already makes the simple COLRv1 test .glyphs pass "output is identical" in ttx-diff.